Juan Pujol Garcia

Juan Pujol Garcia was a Spanish double agent during World War II who worked against Nazi Germany.  During the Spanish Civil War, Garcia developed a hatred of the communist and fascist regimes in Europe.  This motivated him to become a spy for the Allies.

Juan Pujol Garcia, a Spanish
double agent during WWII 

Pujol was wildly unsuccessful at first.  He was rejected by both the British and Americans when he contacted their intelligence agencies.  However, Pujol was not deterred and decided to apply for a position as a German spy.  He pretended to be a Spanish government official who was fanatically pro-Nazi.  He spun lies about the information he could provide and his love for Hitler.  The German intelligence agency was very impressed, and Pujol successfully became a German agent.Pujol was instructed to travel to Britain to recruit more agents and collect intelligence; instead, he traveled to Lisbon.  To fool the Nazis, he invented several imaginary sub-agents as a fall-back.  He could blame the sub-agents for things that went wrong but take credit for the things that went right.  The Germans even paid some of these fictitious agents a salary.
Eventually, Pujol was accepted as an Allied spy, and he had assistance in managing his network of fictitious agents.  He reported a number of false invasion alerts, wasting Nazi manpower and money, but he included just enough true information to keep the Nazis' trust.
Pujol was critical to the success of Operation Fortitude.  In order for the Allied attack on the beaches of Normandy to be successful, they had to convince the Nazis that they were attacking elsewhere.  Pujol's misinformation, combined with the Allied efforts at deception, persuaded the Germans that the main attack would take place in Calais, 200 miles to the north of where it would actually take place.

Operation Fortitude was a massive Allied attempt at misdirecting
the Germans.  The Allies set up rubber tanks and fake weapons
at various locations to fool the Germans

When the Allies stormed Normandy, the Nazis held most of their forces at Calais, believing the real attack was coming at any moment.  The counterattack was also diverted in this manner; when Hitler sent the Panzers - a unit of armored tanks - to Normandy, Pujol sent an urgent letter claiming his fake invasion was imminent, and that deploying the Panzers would play into the Allies' hands.

On D-Day, Allied forces stormed the beaches of Normandy in five different locations,
code-named Juno, Utah, Omaha, Gold, and Sword

Pujol's work as a double agent had saved thousands of Allied lives and turned the tide of the war.  Pujol had the unique honor of receiving military awards from both sides of the war.  He received the Iron Cross from Germany and was awarded the Most Excellent Order of the British Empire.  Pujol faked his death from malaria in 1949, fearing retaliation from Germany, and the Nazis believed that he died a hero.